High pressure base-catalyzed oligomerization of ketones

Abstract

The base-catalyzed reaction between acrylamide and acetone is studied at various pressures. In the lower pressure range up to 300 MPa, a Baylis–Hillman adduct is produced in low yield. Under 900 MPa, viscous liquids are obtained which are shown to be oligomers of acetone resembling polyacetals. Acrylamide serves as a stabilizing end-capping agent. The reaction can be extended to other keto compounds. The oligomers produced in this way are not stable.

The structure of the oligomers appears complex. The mechanism is supposed to involve the formation of the intermediate zwitterionic Baylis–Hillman species which would add to acetone followed by anionic propagation. Another possibility is an initial aldol reaction followed by oligomerization. Pressure would be a highly beneficial parameter promoting ionogenesis.

Keywords:

• High pressure chemistry
• Baylis–Hillman reaction
• Acrylamide
• Polyacetals
• Electro-striction

Acknowledgements

The author is greatly indebted to Caroline Dietrich (Université Louis Pasteur) for skilful IR spectra recording and literature screening.